This is a continuation in part of Ser. No. 504,144 filed Sept. 9, 1974 which is a continuation of Ser. No. 338,640 filed Mar. 6, l973, both of which are now abandoned.
This invention relates to an improved mold for continuous casting process wherein the cooling capacity and thermal conductivity of the mold are controlled to enable casting of a sound metallic material, that is, the surface does not need to be conditioned.
In known continuous casting molds, a mold is made of copper in view of the thermal conductivity and mechanical strength thereof. It is well known that the cast metal surface, especially steel, requires conditioning, e.g. scarfing, since many surface checkings, e.g. tortoise shell patterns or cracks which reach a depth of several millimeters, appear on the cast piece when a large piece of heavy plate of the 40 Kg class or high tension steel of the 50 Kg class is cast. It is needless to state that the above conditioning increases cost of manufacture, lowers yield and brings about other manufacturing losses. Thus, many countermeasures have been carried out to avoid such losses. For example, a Mo or Cr coated mold, or a mold having its lower portion altered with iron, has been developed and used. It is however, well known that many defects exist with the above prior molds. That is, the coating of Mo or Cr on the mold surface is itself troublesome and wear resistance of the coated layer is low. Secondly, the coated layer tends to become stripped. For example, the Mo coating layer strips after being used about 30 heating cycles. In case of Cr coating, even if the coating layer has a thickness of 0.05 to 0.1 mm, the layer strips after about 120 heating cycles. In other words, effect of coating the mold surface is poor in durability. Many technical difficulties are seen in altering the lower portion of the mold with iron, especially such as used for a large slab of more than 40 Kg/cm.sup.2, whatever may be the case at a small bellet. Thus, it is the present situation that a mold is not available which does not disadvantageously influence the surface quality of the cast metal.